Hi,

BS is just a slang for bachelor of science.

BS course is of four years course long and B.sc is 3 years. B.Sc maths is pure maths course which contains topics geometry ,trigonometry, calculus and other theories . BS is specifically designed to stress more on technical components of enducation . B.sc and  BS  are almost similar in outer countries BS  is well known . There are many opportunities  for the students after completing  the  course. They can also pursue M.sc(information  technology) ,MBA  etc.

There is also adual course in iit BS and MS which is 5 years.

All the best!